FIG. 1 depicts a side view of a conventional perpendicular magnetic recording (PMR) head 1 used in recording a PMR media (not shown). FIG. 2 depicts a top view of the conventional PMR head 1. Referring to FIGS. 1-2, the conventional PMR head 1 includes a read transducer 2 and a PMR write transducer 10. The conventional read transducer 2 includes shields 4 and 8 and read sensor 6. The conventional PMR transducer 10 includes a conventional first pole (P1) 12, a first coil 14, conventional auxiliary poles 16 and 20, a conventional main pole 18 having a flared region 19 and pole tip 21, conventional write gap 22, a conventional second coil 24, and shield 26. Although the conventional PMR transducer 10 is depicted with two coils 14 and 24, a single coil may also be used.
In order to write data to a PMR media, the coils 14 and 24 are energized. Consequently, the main pole 18 is magnetized and the media written by flux from the pole tip 21. Based on the direction of current through the coils 14 and 24, the direction of magnetic flux through the main pole 18 changes. Thus, bits having opposing magnetization can be written and the desired data stored on the PMR media. When the conventional PMR transducer 10 is not writing, no current is driven through the coils 14 and 24.
The conventional PMR head 10 is desired to be used at higher recording densities. In such applications, domain lockup, also termed remanent erasure, can be an issue. Domain lockup occurs when the conventional PMR transducer 10 inadvertently erases data in the PMR media when no current energizes the PMR head 10. This occurs due to a remanent field remaining the main pole 18. Domain lockup is sensitive to the shape anisotropy of the pole tip 21. A long nose length, NL, or the length of the pole tip 21 from the air-bearing surface (ABS) to the flaring point of the flared region 19, is more likely to cause domain lockup. Without lamination of the main pole 18, the nose length typically is no greater than about twice of the physical track width (perpendicular to the page in FIG. 1). Consequently, most PMR transducers 10 have a short nose length. For such PMR transducers 10, the primary cause of pole erasure is the magnetic domains in the yoke that may not fully relax after writing. Stated differently, the main pole 18 may not completely demagnetize after writing. Further, the pole tip 21 is sufficiently small that such deviations of the magnetization domains in the main pole 18 from a perfectly demagnetized state may produce significant magnetization in the pole tip 21. As a result, a high remanent field may be present in the PMR media even when no current is driven through the coils 14 and 24. This remanent field may erase data recorded on the PMR media after the head 10 passes over the media for many revolutions. Because it involves this inadvertent erasure, domain lockup is undesirable. Further, domain lockup may also result in other issues, such as catastrophic failure of the hard drive if the servo areas are erased by the remanent field of the conventional PMR transducer 10.
In order to reduce the remanence of the conventional main pole 18, the width, w, of the conventional main pole 18 may be large. For example, the width, w, may be on the order of ten through twenty microns. Although the remanent field of the main pole 18 is reduced, during writing, magnetic charges 30 may be developed on the auxiliary pole 16 and/or 20. Such charges 30 produce a significant off-track field. The off-track field may inadvertently write to the other tracks not desired to be written. Stated differently, the auxiliary pole 16/20 may produce a field that causes adjacent track erasure. Thus, performance of the conventional PMR head 1 may still be adversely affected.
In addition, the conventional auxiliary poles 16/20 are also recessed from the ABS by a relatively small amount. For example, in some conventional PMR transducers 10, the front portion of the auxiliary poles 16/20 is recessed from the pole tip 21 by approximately one-half to one micron. Because of the small size of the recess, the conventional auxiliary pole 16/20 may be capable of delivering a large flux to the conventional main pole 18. However, the large amount of magnetic flux delivered to the conventional main pole 18 causes the write field for the conventional PMR head 10 to increase with increasing current. Stated differently, the field in the pole tip 21 may be larger than desired. Consequently, the write width is increased, adversely affecting the track width. In addition, this makes effect it more difficult for the drive using the conventional PMR head 1 to optimize the write current.
Accordingly, what is needed is a system and method for reducing domain lockup in a PMR head substantially without unduly sacrificing performance.